Many contemporary electronic devices have the facility to connect with external or peripheral devices for transfer of audio signals. For instance, mobile telephones, tablets, laptop computers, mp3 players and the like are examples of electronic devices that are operable with peripheral audio devices such as a headset, for example, that is external to and distinct from the electronic device. A peripheral device such as a headset may typically comprise mono or stereo speakers for audio playback and possibly a microphone for voice communication.
Such external peripheral audio apparatus has often been connected via a mating connector such as a plug and socket arrangement for transfer of analogue audio signals. For instance, many audio peripherals such as headsets have a jack plug such as a 3.5 mm jack plug for connection to a suitable jack socket on the host electronic device. A well-known arrangement for a jack plug and its associated socket is TRRS (Tip-Ring-Ring-Sleeve), which has four contacts for left audio, right audio, microphone, and ground. This allows for transfer of two channels of analogue audio data from the host device to the peripheral and/or transfer of a channel of analogue audio data from the peripheral microphone to the host device.
Increasingly it is becoming desirable to allow for digital audio data transfer between the host device and a connected peripheral. Various digital data interfaces are known, such as USB.
Digital data transfer protocols, such as the USB 2.0 specification or later specifications, can provide for transfer of digital data at relatively high data rates, which means that such interfaces can be used for transfer of relatively large data files, such as high quality video files for example. However historically USB and associated software stacks in the Android™ operating system in particular, commonly used on some electronic devices such as cellphones, were never developed with the aim of streaming time-critical audio data and, the latency associated with the digital signal path established, i.e. the time taken for a digital signal to propagate from a source to a destination via the digital signal path, may be undesirably high for some such audio applications.